The reason why Diddy has "Nintendo" written across his hat is because when Rare was developing the DKC games, they gave Dixie Kong a Rare logo pin atop her hat and Diddy a cap with the Nintendo logo on it to signify that Dixie was property of Rare's and Vice Versa with Diddy Kong and Nintendo. Since modern DKC games have fallen into the hands of Retro Studios (I'm pretty sure that's the name), the Rare pin has been removed from Dixie's hat ever since, and Diddy's Nintendo hat is all that remains of Rare and Nintendo's interloping pasts